Circuit protection



Nov. 25, 1930. v BIERMANNS 1,783,105

CIRCUIT PROTECTION Original Filed Aug. 24 1925 Irv/enter; Josef Biermemns,

by H is Attorney.

Patented Nov. 25, 1930 UNITED STATES PATENT OFFICE JOSEZE BIER-MANNS, OF KARLSHORST, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK CIRCUIT PROTECTION lApplication filed August 24, 1925, Serial ltd-52,143, and in Germany September 16, 1924. Renewed April 18, 1930.

My invention relates to circuit protection, and more particularly to improvements in protective systems and apparatus for controlling an electric circuit on the Occurrence of abnormal conditions with a discriminating action dependent on the impedance and more particularly the reactance or the resistance component of the impedance potential drop of the circuit to be protected whereby a faulty portion or section thereof can be disconnected selectively without interrupting continuity of service on the remainder of the circuit.

In a faulty line or circuit, the ratio of the potential to the current increases continuously from the point ofgfault to the source, since the potential 6 is smallest at the point of fault and largest at the source while the current 2' is the same at all points. Relays which operate when this ratio falls below a certain value are known and by taking into consideration the resistances, reactances or impedances of the individual sections of the system, this value canrbe selected so that the circuit interrupting means nearest the fault on each side thereof are actuated with reasonable certainty. It is difficult, however, perfectly accurately to adjust the relay and accurately to maintain this adjustment. If the adjustmentis made for too low an ohmic value, a line section subjected to a fault such as a short-circuit may not be disconnected while if for too high an ohmic value two sections are overlapped and both may be disconnected.

In accordance with my invention, this defeet is remedied by arranging the protective device for operation at different values of the ratio of the potentiale to the current 2'. For example, two relays can be used, one of which is adjusted for an ohmic value less than that of the section to be protected and is arranged to release an over-current relay set to operate after a predetermined period which for purposes of explanation may be assumed to be onev second and the other of which is adjusted for an ohmic value greater than that of the section and is arranged to release an over-current relay set to operate after a greater time period, for example, two

: seconds. In order to avoid doubling the number of relays, I provide in accordance with my invention a single relay, comprising a movable member which is arranged to take a position dependent on the relative values of the current and potential, such that the line is disconnected in a predetermined time which remains fixed for any given value of current and is independent of the ratio of the potential to the current when the ratio lies within predetermined limits, the higher of which is determined by or corresponds to the ohmic resistance, reactance or impedance of the section, and in a longer time when the ratio is greater than such higher limit.

For a still greater value of the ratio, the

line is not disconnected at all. The number of ranges for the ratios is not limited and the ranges themselves are flexible. When two ranges are used as set forth above, the

higher limit of the range giving the shorter time should conform to the length of the line section to be protected. The higher limit of the range giving the greater time is some what restricted in order to avoid disconnection of a sound section next to a faulty section but it may be chosen so large as to include substantially the resistances of the section to be protected and the next followmg section.

Inasmuch as the resistance may vary with vary even with the fault at the same location.

This variation may effect the disconnection of the wrong section but the uncertainty can be avoided by using the reactive con'iphncnt 5 sin 6 of the potential instead of the resistance component 6 cos 6, since the former remains substantially unaffected by the arc.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the accompanying drawing Fig. 1 illustrates partly in diagram and partly in perspective an embodiment of my invention and Fig. 2 illustrates schematically a dynamom- "blv shaved discs such as ouadrant's ,7, v which are mounted on asingle shaft 8. lnach of a fault.

eter type of moving coil ohm meter that may be used in carrying out my invention. 7

In the embodiment of my invention shown in 1, an electric line or circuit 1 is arranged to be controlled by a suitable circuit interrupter '2 through a trip coil 3, the circuit of which is controlled by a protective device comprising two elements such as an ohm disc has a driving element or magnet of thel pnase displacement type; V The dri ng element ofthe disc 6 comprises cooperating current and otential windings 9 and 10 respectively arranged to be energized from, the circuit 1 through current and potential trans- V formers 11 and 12. ,Where it is desiredto employ the reactance component of the potential, the constants of the circuits of the current and potential windings Qand 10am g V l v tour and asv shown COIHPIISQS two sections whose angular extents aredesignatedA and A and wh ch have different radn. Obviso chosenas tocarry currentswhicn are in phase when there is non-inductive load on tfhe circuit. p 1

The driving element-for the disc 7 comprises cooperating current windings 13. and 14 connected to be energized from the current transformer 11. Thedisplacement of tie currents in these windings may be obtained in suitable manner, as for example, by a resistance loconnected in series with the winding let.

n w, K1 and K1 represent constants,

position or displacement from an arbitrary reference line of the discs 6 and 7, and i, e and 6 the current and potential of the line land the phase angle between them, then because of the shape of the discs and the con struction and arrangement of the parts, the torques T5 and T on the discs 6 and 7 respcctively are The shaft 8, being left to itself, conres to a position of rest or state of equilibrnnn through the equalizat on of the torques in an angular position which is dependent upon the relative values oflthe current and potential of the circuit, thus:

Where it is desired to employ the resistance may be of any suitable type.

' the short radius section is in this path.

for any position of the member 22 within the. angular range A and a given current, the contacts Wlll be closed 1n a shorter time than 7 b) functions of the angular;

' ra A have both contacts movable by the relay 5,

component of the potential, the constants of the circuits of the current and potential windings 9 and 10 are so chosen as to carry currents displaced 90 in phase relation when there is non-inductive load on thecircuit. In this case, in the above formulae cos 6 will replace sin 9. V

The over-current time element or relay 5 This relay has its Winding 17 inseries relation with the line 1 through the current transformer 11.

Forp'u poses of illustration, the time action i issho'wn as being obtained by a step-up gear drive 18 on a fan wheel 19. For controlling the circuit of the trip coil 3 in accordance 'withthe'combined action of the ohm meter d and the relay 5, relatively movable'coope'n ating members such as contacts 20 and 21 are mounted on a pivot and arranged to be actuated by the relay 5 In order to control the closing of'the contacts20 and21 in accordance with the double ranges heretofore descrlbed, a member 22 1s secured to the shaft 8 so as to be for certain angular positions of the shaft inthe path of movement of the contacts 20 and 21. This movable member 22 may be ofarcuate conously, for a given current, relative movement of the contacts, that is to say, closure thereof, will occur morequickly when the longer radius section ofthe member 22 is in the path of movement of the contacts 20, 21, than when Thus,

when themember 22 is within the angular Obvlously, 1t is not necessary to since the member 22 could of itself constitute the contact 20. Closure of the contacts Y20 and 21 can only occur when the shaft 8,

the position of which is determined by the relative values of the current andpotential "of the circuit, sets the member 22 in the path be protected, while'for the angular range A values greater than'that of the section would govern. V p p 7 Theohm meter 4 shown in F 1g. 1 is of the shown schematically in Fig. 2 may be used.

. Thistype comprises two fixed coi1s2et'and which are arranged substantially perpendicularlyto each other and a movable coil 26. The fixed coils 24 and 25 would be coninduction disc wattmeter type but other types of ohm metersuch as the moving coil type nected to be energized respectively in accordance with the current 2' and the reactive component 6 sin 6 of the potential of the circuit and the moving coil 26 would be connected to be energized in accordance with the current in the circuit. The sine component is obtained when with the noninductive load on the circuit the currents in the fixed wind ings 24 and 25 are displaced by 90.

By virtue oi the magnetic forces existing between the fixed coils and the movable coil, the torques exerted thereon position the movable coil so as to establish equilibrium. The torques T, between the coils 2e and 26 and T between the coils 25 and 26 are:

The angular position of the movable coil 26 resulting from the balancing of these torques is dependent upon the relative values of the currentand potential of the circuit, thus:

K 'i cos 5 =K ei sin 6 sin (,5

cos ei sin 0 Sin 1) 1 2 cot =K What I claim as new and desire to secure by Letters Patent of the United States is 1. A protective device comprising a time limit relay, an ohm meter and movable members respectively arranged to be actuated thereby, characterized by the fact that one of said members is arranged for movement in the path of movement of the other and is so shaped that for predetermined ranges of movement different definite movements of the other are permitted.

2. A protective device comprising relatively movable cooperating contacts, an overcurrent time relay for actuating said contacts and an ohm motor having a member movable in the path of movement of said contacts characterized. by the fact that said member is so shaped as to permit relative movement of the contacts by the over-current relay in a time dependent on the current and the position oi the member.

3. In combination with an electric circuit and circuit interrupting means therefor, relay means comprising winding connected to be energized in. accordance with the current in said circuit and a winding affected by the potential of said circuit arranged to control said interrupting means in a predetermined time, and means for maintaining the time lined for any given value of current inde pendently of the ratio of the potential to the current when the ratio lies wit iin predetermined limits and for permitting a longer time when the ratio is greater than the higher of said limits.

4:. In combination with an electric circuit and circuit interrupting means thcrcf means for controlling said interrupt-cg means on the occurrence of a fault compris ing a time limit relay and 111 ohm meter including means arranged to control the opening of said interrupting means in predetermined time, which remains fixed for any given value ot current and is indepen dent of the ratio oi the potential to the current when the ratio lies within predetermined limits and in a longer time when the ratio is greater than the hi her or said limits.

5. A protective device for an electric circuitcomprising relatively movable cooperating contacts, a relay having a currentresponsive winding for actuating said contacts, and an ohm meter comprising a movable member adapted to take a position dependent on the relat've values of the current and potential ot the circuit at the point where the device is located and. arranged on the occurrence ot a fault to take a position in the path of movement of said contacts whereby to permit relative movement thereof by said relay in a predetermined time dependent on the current when the ratio of the potential to the current is less than a predetermined value and in a longer time when the ratio is greater than such predetermined value.

6. In combination with an electric circuit, a protective device comprising relatively movable cooperating contacts, an over-current time relay for actuating said contacts, and an ohm meter having a movable member adapted to take a position dependent on the relative values of the current and potential of the circuit at the point where the device is located, said member being constructed and arranged on the occurrence of a fault to take a position in the path of movement of said contacts dependent on the location of the fault whereby relative movement of the contacts is effected by the over-current relay in a time wlich is dependent on the current and is shorter, when the ratio of the potential to the current is less than a predetermined value, than the time when the ratio is greater than such predetermined value.

7. In combination with an electric circuit a protective device comprising relatively movable cooperating contacts and means for actuating said contacts comprising an over-current time relay and an ohm meter having a movable member adapted to take a position. dependent on the relative values of the potential and current of the circuit, said member being mounted in the path of movement of said contacts and shaped so that for a predetermined angular range oi positions the time necessary to close the contacts is substantially constant for a predetermined value 01 current and for another predeter ill] 4. V i i nreaioe mine-d angular range the time is longer and 1 substantially constant for the same value of current. V

8. In combination with an electric line, a

protective device comprising relatively movable cooperating contacts andmeans for actuating said contacts comprising a time element relay and an ohm meter having a movable member adapted to takeaposition depen lent on the relative values of the current and potential of the line at the point where the device is located and arranged to permit relative movement of said contacts by -j the time element relay only when the ratio of the'potential to the current is within predetermined limits either side of the impedance oi b11 line section with which the device is associated.

9. A protective device comprising relative ly movable cooperating elements and means for controlling said elements including a time relay and an ohmmeter and means controlled by said ohm meter for permitting the completion of the relative movement of said elements in a fixed time throughout one range in movement of the ohm meter and in different fixed time throughout another range in movement-of the ohm meter V p 7 10. In combination with an electr c circuit and circuit interruntino' means therefor re i e: v

lay means computing a winding connected to be energized in accordance with the current in said circuit and a winding affected by the potential of said circuit arranged to control said interrupting means in a predetermined time and means for maintaining the time fired for faults within a predetermined distance of the relay means and for permitting a longer fixed time when faults occur at a greater distance from the relay means.

11. Aprotective device comprising relatively movable cooperating contacts and controlling means therefor including a time relay and an ohm meter and means controlled by said ohm meter for effecting a circuit controlling operation of said contacts in a fixed time throughout one range in movement of the ohm meter and in a ditiere'nt fixed time throughout another range in movement of the ohm meter.

12. A protective device comprising relatively movable cooperating contacts and controlling means therefor including a time relay and an ohm meter, and means controlled by said ohm meter for etl'ecting a circuit controlling operation of said contacts in a fixed time throughout one range in movement of the ohm meter and in a different fixed time throughout another range in movement of the ohm meter, and for preventing circuit controlling operation when the movemen o1 the ohm meter is outside one of said ranges.

In witness whereof, I have hereunto set my hand this 8th day of August, 1925.

JGSEF BlERlHANNS.

Certificate of Correction Granted November 25, 1930, to

JOSEF BIE RMANNS.

Patent No. 1,783,105.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 16, for the first line of formula T=K i cos 11 read T =K i 00s b; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 6th day of January, A. D. 1931.

[SEAL] Y M. J. MOORE, Acting Commissioner of Patents.

Patent No. 1,783,105.

JOS'EE BIERMANNS.

It hereby certified that error appears numbered patent requiring correction as of formula T=K i cos 5 read T =K i 00s b;and that the said Letters Patent should be read With this correction therein of the case in the Patent Oflice.

Signed and sealed this 6th day of January, A. D. 1931.

[SEAL] M. J. MOORE,

Acting Commissioner of Patents.

Granted November 25, 1930, to

in the printed specification of the above 4 follows: Page 3, line 16 for the first line that the same may conform to the record 

